Stimulation of phosphoinositide hydrolysis by glyceraldehyde-3-phosphate in electroporated HIT-T15 cells.

HIT-T15 cells labeled with myo-[3H] inositol were permeabilized by electroporation and subsequently stimulated with various glycolytic intermediates in the presence of 20 mM LiCl in a buffer mimicking cytosolic ionic composition. Of the various glycolytic intermediates tested, only D-glyceraldehyde-3-phosphate (G3-P) stimulated the formation of labeled inositol phosphates. The half-maximal response to G3-P occurred at a concentration of 0.75 mM. Formation of inositol phosphates in electroporated cells was also observed in response to GTP. G3-P further potentiated the formation of inositol phosphates in response to GTP, however, the interaction between G3-P and GTP was additive rather than synergistic, indicating that G3-P stimulates phosphoinositide hydrolysis in a manner different than the receptor mediated GTP-dependent activation of phospholipase C. The potentiation of the GTP response by G3-P did not appear to involve inhibition of the GTPase activity of a phosphoinositide-specific G protein, since G3-P also potentiated the formation of inositol phosphates in response to GTP-gamma-S or NaF in a nearly additive manner.